How to Lose Weight and Build Muscle at the Same Time

Gaining strength while burning fat isn't easy to do, but research shows that it is possible.

Losing fat and gaining muscle at the same time can seem like an impossible task. To lose fat, you need to be in a calorie deficit. To gain muscle, you need to be in a calorie surplus. It’s just not humanly possible for both things to happen at once. Others claim it can be done, but only if you take steroids, or follow a fancy carb cycling protocol, the instructions for which are more complicated than the blueprints for a nuclear power station.

So who's right? Although there are lots of ifs, buts, and maybes, it is in fact possible to lose fat and gain muscle at the same time. Not everyone can do it, and not everyone can do it to the same degree—but there are many studies that document fat being lost and muscle being gained simultaneously. Here's how you go about it.

The first and most important step is to put yourself in a calorie deficit. There are lots of different ways to achieve that, from intermittent fasting or keto to just cutting down on the junk you know you shouldn’t be eating. But no matter how you go about creating that deficit, you most definitely need to be in one if fat is going to be lost.

You’re said to be in a “calorie deficit” when there is less energy coming from the food you eat than your body needs to move, pump blood around your body, break down and synthesize new muscle protein, along with all the other stuff involved in keeping you alive. When you’re in a calorie deficit, there is a gap between the amount of fuel your body needs and the amount it gets from food. So, it starts looking for something to fill that gap. In most cases, that “something” will be the large pool of chemical energy—aka, fat—stored in your body.

Second, you will need to be an overweight beginner. By that, I’m talking about someone who is walking around with a significant chunk of body fat and is new to lifting weights. When you first start weight training, your body is highly responsive and can add muscle very quickly. In fact, researchers from the United States Sports Academy found that a group of overweight beginners lost over 16 pounds of fat and gained almost 10 pounds of muscle during a 14-week training program.

In other words, they gained a decent amount of muscle while also losing slightly more than one pound of fat per week. When calories were cut, there was still plenty of stored energy available to supply their muscles with the fuel required to grow. Being an overweight beginner means you can get away with a lot. Even with a highly restrictive liquid diet containing less than 1000 calories a day, weight training still led to an increase in muscle size in a group of obese women.

In short, if you haven’t touched a weight in your life, you’re going to have a much easier time dropping fat and replacing it with muscle. But as you get leaner, things become progressively more difficult. A bodybuilder, for example, who is closing in on the upper limits of his natural muscular potential, is doing well just to hold on to the muscle he currently has while getting shredded for a contest.

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In one case study, researchers followed a 21-year old male bodybuilder as he prepared for a contest. Over a period of 14 weeks, he cut his body fat in half, dropping from 14% to 7.2% body fat. However, almost half of that lost weight came from lean body mass. In other words, he lost rather than gained muscle. That’s despite the fact he was doing a lot of the things that are supposed to help you retain muscle—eating plenty of protein, lifting weights four times a week, and doing interval training.

For anyone in this type of condition, the main benefit of strength training during fat loss is to retain rather than gain muscle mass. What this means is that you’ll need to modify your expectations as your body composition changes. All other things being equal, you’ll find it easier to build muscle while losing fat when you’re going from “overweight” to “lean” than you will going from “lean” to “ripped.”

If you’ve been lifting weights for some time, the speed at which you gain muscle will have slowed down. And it doesn’t matter how many supplements you take, what type of complicated carb cycling protocol you use, or how many muscle-building “hacks” you try, muscle just isn’t going to be gained that quickly once you’ve moved past the beginner stages of training. On a related note, anyone who’s been in shape before will find it easier to build muscle and lose fat simultaneously when they return to training after taking a few months off.

In a study of elite rugby union players returning after the off-season break, four weeks of pre-season training led to three pounds of fat being lost and over four pounds of muscle being built. That’s because of a phenomenon known as muscle memory. When muscle is gained, lost, and then re-built, it will grow more quickly during the re-building phase compared to the initial training period from an untrained state.

Next up is protein. If you want to lose fat and gain muscle, you’ll need to eat enough protein. Other than lifting weights, getting a sufficient amount of protein in your diet is probably the single most important thing you can do to gain muscle while losing fat. Researchers at McMaster University discovered as much in a 2016 study.

They rounded up a group of young men and put them on a month-long diet, where they ate just 60 percent of what they’d normally need to maintain their weight. Alongside the diet, the men also trained hard six days a week, lifting weights and doing intervals, as well as various other forms of intense exercise. Half the men ate a protein-rich diet, getting around one gram of protein per pound of bodyweight per day. The rest of the group received just half that amount.

As you’d expect, both groups lost fat. Men in the high protein group, however, were the only ones to gain muscle, finishing the study with an extra 2.5 pounds of muscle mass. While the low protein group didn’t lose muscle, they didn’t gain any either. To sum it all up, it is possible to lose fat and build muscle at the same time. Even when you’re in a calorie deficit, lifting weights and eating enough protein will allow for muscle to be gained, or at the very least retained, while you drop fat.

While you can do both at the same time, however, it's highly unusual to do both at the same rate. That is, unless you’re an overweight beginner, returning to exercise after a layoff, very genetically gifted, or you’re on the sauce, you won’t build muscle at anything like the same speed at which you lose fat.

There are a number of carb cycling methods that claim to be able to get around the problem, but even then you’re not going to replace every pound of fat lost with one pound of muscle. The best that most people can hope for is to generate a small amount of muscle gain while losing a much larger amount of fat.

In other words, it’s far more realistic to drop 10 pounds of fat while gaining a pound or two of muscle. Losing 10 pounds of fat at the same time as replacing it with 10 pounds of muscle, however, is not an attainable goal for most people most of the time.

Christian Finn is a UK-based personal trainer who holds a masters degree in exercise science.

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